We would like to purchase a microcomputed tomography (micro-CT) system for the Hospital for Special Surgery to acquire high resolution morphometry and density information from bone samples. Several NIH- sponsored investigators at our institution and at other academic institutions in New York City are studying bone development, repair, and adaptation. For these investigators, understanding skeletal integrity (the biological, chemical, and mechanical influences that make bone such a distinctive tissue) is a fundamental part of their research. Taking advantage of advances in molecular biology and genetics, these researchers are integrating biology and engineering into in vivo experiments using small anhnal models to examine the relation between composition, structure, and function that allows the skeleton to fulfill its unique role. The purchase of a micro-CT system will provide crucial detailed structural information on the small bones from these animals that will complement compositional measurements (from infrared imaging) and functional data (from mechanical testing and finite element analyses). For example, the ability to resolve morphomet:ric details at nearly the same resolution (<20 microns) with micro-CT as we are able to resolve mineral and matrix compositional properties (< 10 microns) with infrared imaging creates unique capabilities to examine composition-structure-function relations in trabecular bone at ultrastructural levels of tissue organization. The value of micro-CT has been demonstrated in preliminary studies in which time has been borrowed on a system in The Netherlands. However, the large number of investigators who could benefit and the large number of new research questions that will arise by having a system at our institution far outweighs our ability to acquire sufficient time on other systems. The grant for the micro-CT system will be administered within the Core Center for Skeletal Integrity, a new NIH-sponsored center (p30 AR46121) organized under an Administrative Core with research cores in Analytical Microscopy, Infrared Imaging, and Mechanical Testing. The micro-CT system will be housed within the Analytical Microscopy core, and policies and procedures for its use, maintenance, and oversight will follow from those already established for the Core Center. This administrative procedure will insure optimal use, long-term operation, and maintenance of the equipment as part of the institution's commitment to the Core Center.